Showing papers by "University of East Anglia published in 1976"

The utilization of sugars by yeasts.

Abstract: Publisher Summary This chapter outlines the breakdown of sugars by yeasts. To continue biosynthetic processes necessary for growth, yeasts obtain energy from sugars by breaking them down. The energy set free is stored as the “high energy” phosphate derivative adenosine 5’-triphosphate (ATP) that is synthesized as the sugar is catabolized. In catabolism, glycosidic bonds are hydrolyzed to yield component monosaccharides. A low concentration of oxygen is often important for obtaining a high yield of ethanol from certain sugars. Particularly in initial and terminal reactions, differences are found among different yeasts, and such relatively minor biochemical differences are often of considerable practical importance. The information provided in this chapter is based chiefly on studies yeast such as, Saccharomyces cerevisiae , Saccharomyces uvarum , Candida utilis , and Kluyveromyces fragilis . However, the ability of yeasts to utilize sugars is not only of potential value, it can also be a nuisance. Yeasts are notorious as spoilers of foods that contain a high concentration of one or more sugars, such as honey, maple syrup, sugar cane, and confectionery.

Relative Reactivities of Hydroxyl Groups in Carbohydrates

Abstract: Publisher Summary This chapter discusses the important reactions of the hydroxyl group. Knowledge of the relative reactivities of hydroxyl groups in carbohydrates is fundamental to a thorough understanding of carbohydrate chemistry. The chapter explains esterification, which forms the largest part of the literature since 1953 on selective reactions of carbohydrates. The common methods of esterification utilize an acid chloride or an acid anhydride as the reagent, but other acid derivatives often show different selectivities. An investigation pertinent to the subject of favored reactivity concerned the reactions of certain acyl halides with ethanol, in acetone or chloroform solution. The mixed-order nature of some of these reactions suggested that every rate-determining transition-state contained the substrate, the nucleophile (ethanol), and an acceptor— X—for hydrogen bonding, suitable acceptors being an acetone molecule, a chloride ion, or another ethanol molecule. The possibility that intramolecular hydrogen-bonding does not persist in pyridine and that the advantage of a bonded hydroxyl group would be lost, invalidates the explanation of favored reactivity. But if the hydrogen-bonding to pyridine is hindered in the transition state, intramolecular hydrogen-bonding could conceivably assume importance.

Time Series Modelling and Interpretation

Abstract: SUMMARY By considering the model generating the sum of two or more series, it is shown that the mixed ARMA model is the one most likely to occur. As most economic series are both aggregates and are measured with error it follows that such mixed models will often be found in practice. If such a model is found, the possibility of resolving the series into simple components is considered both theoretically and for simulated data. 1. INrRODUCTION THE recent publication of the book by Box and Jenkins has greatly increased interest by time series analysts and econometricians in more complicated, even if more "parsimonious", time series models. However, the intuitive interpretation of the models that arise is not always simple and an applied research worker may well ask how such a model could have arisen in practice. In this paper, the possibility that a complicated looking model could have arisen from a simpler situation is explored and some suggestions made about the possible interpreta- tion of some models that appear to arise in practice. The only series to be considered are those with zero means and generated by models with time-invariant parameters. Thus, possibly after an appropriate linear transformation, the series will be taken to be second-order stationary. Let Xi be such a series, so that E{X} =O, all t.

Meiotic drive for B-chromosomes in the primary oocytes of Myrmeleotettix maculatus (Orthopera: Acrididae).

Abstract: Using a modified technique which allowed observation of chromosome orientation in the primary oocyte of grasshoppers at the onset of anaphase, it has been possible to establish that the B-chromosome is distributed preferentially on the egg side of the metaphase plate rather than the polar body side. The frequency of this preferential orientation matches very closely the level of preferential transmission determined from breeding experiments using individuals from the same population. The spindle is asymmetrical in the primary oocyte of this species, and a possible explanation of the meiotic drive is proposed as a result of the conical shape of nucleoplasm surrounding this spindle. The autosomal chiasma frequency of these females is generally lower than comparable males and is increased by the presence of B chromosomes; but the chiasma frequencies of the sexes respond differently to the addition of 1 and 2 B-chromosomes.

The propagation of surface waves in bodies with material boundaries

Abstract: A study is made of the propagation of Love and Rayleigh waves in elastic bodies whose boundaries support surface stresses, such as crystals cleaved in vacuo or bodies upon which are deposited extremely thin films. The surfaces of such bodies are herein modelled as two-dimensional elastic continua that adhere without slipping to their substrates and in which is located residual stress. The corresponding boundary condition gives rise to behaviour which is contrasted with that occurring in the absence of surface stress. The results are also related to previous studies of surface waves in thin strata superposed on elastic half-spaces, from which the present theory differs by taking into account residual stress. The behaviour is shown to be sensitive to the relative values of the residual stress, elastic moduli, and density of the surface. Attention is drawn to the relevance of the study to those signal-processing devices which utilize surface waves in thin films.

Transfer of SO 2 and other reactive gases across the air-sea interface

Abstract: Using results obtained from experimental studies of the atmospheric transport of sensible heat, water vapour and momentum over the sea, deposition velocities of soluble and reactive trace gases are evaluated. The deposition velocities that result vary with the height of observation; they are nearly linearly dependent upon wind speed and are a function of the prevailing stability regime. In near-neutral stratification, it appears best to take the deposition velocity to be about 0.13 % of the wind speed when observations are made at 10 m height. When data are collected at 1 m height, this factor becomes about 0.2 %. Although the evaluations are intended to apply particularly to the case of SO 2 transfer, consideration of the molecular diffusivities of other gases that are similarly reactive (e.g., NH 3 , HC 1 , NO 2 and SO 3 ) suggests that less than 10 % error will result from adopting the present results for SO 2 for these gases as well. When the liquid phase resistance is important, as is the case for CO 2 for example, then the deposition velocities are decreased to a limiting lower value specific for each gas. The present model considers only the simpler case in which the liquid phase resistance is negligible. DOI: 10.1111/j.2153-3490.1976.tb00683.x

Spectral analysis and the astronomical theory of climatic change

Abstract: THE astronomical theory1 attributes long term changes in climate to changes in the Earth's orbital geometry. This theory has become increasingly accepted in recent years. To this acceptance, workers associated with the CLIMAP project have added exceptionally strong support2 using spectral analysis of deep-sea core data. They have linked periodicities in the Earth's orbital parameters with periodicities in deep-sea core parameters related to sea-surface temperature, ice volume and oceanic salinity. Their argument rests on the assumption of a linear response between input (radiation changes caused by changes in orbital geometry) and output (the climate-dependent parameters mentioned above). At the same time they have attributed the anomalously high variance associated with the longest periodicity (∼ 100,000 yr) to a nonlinear response. There is no contradiction here because the response function, the climate ‘black box’, most probably has both linear and nonlinear components. I examine here the question of nonlinear response in more detail.

Geometry of river meanders

Abstract: THERE are many factors affecting the geometry of rivers. Width, depth, slope, flow velocity and plan shape are all influenced by discharge, sediment load, sediment types, and valley slope through the operation of the continuity, flow resistance, bed load, bank competence and meander equations. If each of these equations could be determined accurately then their simultaneous solution would define the three-dimensional geometry of alluvial channels1,2. Although the equations cannot be specified accurately the basic mechanical principles underlying most of the relevant processes are understood. The one exception is the process responsible for plan geometry. Indeed, many theories have been presented to explain the development and maintenance of these patterns, with varying degrees of success. I show here that meander arc length may be a unique function of channel width.

Surface and interfacial waves of arbitrary form in isotropic elastic media

Abstract: A method due to Friedlander of accommodating disturbances of arbitrary form into the theory of surface waves in a semi-infinite isotropic elastic body is extended and shown to yield a simple closed form solution for the displacement field. An analogous treatment of interfacial waves of arbitrary form at a plane contact discontinuity separating different isotropic elastic materials is also given.

Biochemical studies on the nit mutants of Neurospora crassa.

Abstract: One allele at each of the five nit loci in Neurospora crassa together with the wild type strain have been compared on various nitrogen sources with regard to (i) their growth characteristics (ii) the level of nitrate reductase and its associated activities (reduced benzyl viologen nitrate reductase and cytochrome c reductase) (iii) the level of nitrite reductase and (iv) their ability to take up nitrite from the surrounding medium. Results are consistent with the hypothesis that nit-3 is the structural gene for nitrate reductase, nit-1 specifies in part a molybdenum containing moiety which is responsible for the nit-3 gene product dimerising to form nitrate reductase, nit-4 and nit-5 are regulator genes whose products are involved in the induction of both nitrate reductase and nitrite reductase and nit-2 codes for a generalised ammonium activated repressor protein. Studies on the induction of nitrate reductase (and its associated activities) and nitrite reductase in wild type, nit-1 and nit-3 in the presence of either nitrate or nitrite suggest that each enzyme may be regulated independently of the other and that nitrite could be true co-inducer of the assimilatory pathway. Nitrite uptake experiments with nit-2, nit-4 and nit-5 strains show that whereas nit-4 and nit-5 are freely permeable to this molecule, it is unable to enter the nit-2 mycelium.

Nuclear spin‐relaxation studies of hydrated elastin

Abstract: The nuclear magnetic spin-lattice and transverse relaxation processes for the 1H and 2D nuclei in purified elastin (ligamentum nuchae), exchanged and hydrated with excess D2O, have been studied in the temperature range 276°–340°K. The 2D relaxation results clearly show the presence of D2O (1) external to the bulk elastin sample, (2) in spaces within the bulk elastin, and (3) as an integral part of the protein on a molecular level. It is shown from these measurements that the protein on a molecular level. It is shown from these measurements that the water content of the protein itself changes from ∼0.8 g D2O/g dry elastin at ∼280°K to ∼0.2 g D2O/g dry elastin at ∼335°K, a decrease of 400%. The D2O content of the interfiber spaces decreases by less than 20% over the same temperature range. This fact throws considerable doubt on the validity of the values of β, the thermal expansion coefficient of elastin, used by other workers in discussion of the elastic mechanism in elastin. The elastin proton transverse relaxation shows the presence of three regions in elastin having different degrees of molecular mobility. These are assigned to protons associated with the crosslinks, a fairly mobile, hydrophobic, and low-water-content region, and a more mobile higher water-content region. The temperature variation of the relative proportions of these three regions is explained in terms of a hypothetical temperature-composition phase diagram in which the two mobile regions are represented as two partially miscible phases with different negative temperature coefficients of ‘solubility’ in water. The implications of these observations for current views of the nature of elastin are assessed. It is concluded that the spin-relaxation results are consistent with a multiphase structural model for elastin. An approximate sorption isotherm for the water/elastin system is reported and shows the relatively weak nature of the water/elastin interaction.

Synthetic Applications of Heteroaromatic Betaines with Six-Membered Rings†

Abstract: The cycloadditions of 3-hydroxy-1-methylpyridinium betaines with electron-deficient olefins have been extended to a variety of 1-substituents in place of methyl. Application of resonance theory and later of quantum chemical methods led to rationalization of preceding results and prediction of new reactions. Thermal additions of 2π- and 6π-electron addends at the 2,6-positions and of 4π-electron addends at the 2,4-positions are described. The cycloadducts are highly interesting potential synthetic building blocks.

Breeding Biology of the Sylvia Warblers

Abstract: Analysis of nest record cards from the five Sylvia warblers reveals differences in breeding ecology which, despite some overlap in habitat, may permit them to co-exist successfully. Interesting interspecific differences in arrival and timing of breeding season are among other features discussed.

Entropies of mixing of liquid metals A hard-sphere description

Abstract: The entropies of mixing of liquid metals are well explained on the basis of a hard-sphere model in which (i) the total ionic volumes are supposed not to change on alloying and (ii) the observed excess volumes are incorporated into the calculation. The above propositions are illustrated by the consideration of 31 binary alloys in the middle of their composition ranges and of seven such systems across their whole ranges. The formalism also yields a qualitatively correct description of specific heats of alloys in so far as the limited experimental information permits us to judge.

The tradition of appeasement in British foreign policy 1865–1939

Abstract: IF the policy of “Appeasement” is inextricably associated in the historical consciousness with the efforts of Neville Chamberlain's government to preserve peace with the dictators in the 1930s, its origins have been recognized by numerous writers as going back many years before the immediate crises concerning the Sudetenland, Prague and the Polish Corridor. Some have traced its roots to the failure to prevent Japanese aggression in 1931 or Italy's attack upon Abyssinia in 1935; others, with more sense of the positive side of “Appeasement", have focused upon the attitude of the British government and public towards Germany during and after the Versailles settlement; while Mr Gilbert, going a little further back in time, has argued that “appeasement was born” at the moment of the British declaration of war in 1914. Few, if any, commentators have suggested that one should seek the beginnings of “Appeasement” before that event, however.

Relative importance of fungi and bacteria in the decomposition of phragmites leaves

Abstract: The relative importance of fungi and bacteria in the decomposition ofPhragmites leaves was studied in experiments using antifungal and antibacterial antibiotics. Fungi and bacteria were responsible for almost equal proportions of the respiration of the dead leaves after 35 days exposure in a lake, but fungi respired very little after 122 days. The populations of both fungi and bacteria declined between 35 days and 122 days, but fungi declined more. The amount of weight loss ofPhragmites leaves caused by fungi and bacteria was similar after 35 days. Micro-organisms not affected by antibiotics played a significant role in both respiration and loss in weight of leaves.

Effect of mineral precipitation on isotopic composition and 14 C dating of groundwater

Abstract: I PRESENT here a method for determining the combined effects of concurrent mineral precipitation and dissolution on the carbon isotope composition of groundwater. The results are applied to the ‘adjustment problem’ in the 14C dating of groundwater, and are illustrated using published data from the London Basin chalk aquifer. Some 14C ages are changed by more than 10,000 yr.

Pharmacological properties of the adrenergic receptors regulating systemic vascular resistance in the rainbow trout

Abstract: 1. The adrenergic receptors in the systemic vasculature of the rainbow trout have been pharmacologically characterized using an isolated trunk preparation perfused at constant flow. 2. The dominant α-constrictory receptors in the trunk are similar to those of mammals in their adrenaline/noradrenaline potency ratio (3.2/1.0), and in the natures of their blockade by phenoxybenzamine and yohimbine. However they are more selective than mammalian α-receptors, responding directly to only adrenaline and noradrenaline, and not to phenylephrine, methoxamine, dopamine, or isoprenaline. 3. Tyramine and dopamine cause weak α-adrenergic constriction, apparently indirectly through the release of catecholamine stores. 4. The α-adrenergic response is susceptible to inhibition by competitive β-blocking agents, but this effect is due to non-competitive antagonism with a point of action beyond the adrenergic receptor. 5. β-dilatory receptors of the β2, as in the homologous systemic vasculature of mammals, also apparently occur, but their dilatory actions cn only be demonstrated against a background of α-adrenergic vasoconstriction. 6. The racemate d,l-isoprenaline is a more potent vasodilator than the pure isomer l-isoprenaline during α-adrenergic tone because of the competitive α-blocking activity of the d-isomer.

The vegetation of the Samburu–Isiolo Game Reserve

Abstract: Summary (1) Communities were identified in the field from presence/absence records of species using a form of progressive approximation. These communities were then mapped from aerial photographs of the Reserve area and boundaries were later checked on the ground. The quantitative characteristics of the communities were described in terms of cover and frequency. (2) The data were subjected to standard computer analyses and these results are used in an assessment of the validity of the original subjective techniques. (3) A hypothetical scheme is suggested which explains the principal lines of vegetation variation in terms of water availability and soil salinity. A number of related vegetation catenae may be recognized in addition to an east–west trend of increasing tree cover which is attributed to decreasing salinity along the riverine strip. (4) It is concluded that the effects of grazing and burning regimes are superimposed upon those of the physical environment and that further rapid changes in vegetation composition will take place within the next few decades.